%0 Journal Article %A JH Baumann %A SW Davies %A HE Aichelman %A KD Castillo %T Coral Symbiodinium community composition across the Belize Mesoamerican Barrier Reef System is driven by host species and environmental variability %D 2017 %R 10.1101/154179 %J bioRxiv %P 154179 %X Reef-building corals maintain a symbiotic relationship with dinoflagellate algae of the genus Symbiodinium and this symbiosis is vital for the survival of the coral holobiont. Symbiodinium community composition within the coral host has been shown to influence a coral’s ability to resist and recover from stress. A multitude of stressors including ocean warming, ocean acidification, and eutrophication have been linked to global scale coral decline in coral health and cover in recent decades. Three distinct thermal regimes (highTP, modTP, and lowTP) following an inshore-offshore gradient of declining average temperatures and thermal variation were identified on the Belize Mesoamerican Barrier Reef System (MBRS). Quantitative metabarcoding of the ITS-2 locus was employed to investigate differences and similarities in Symbiodinium genetic diversity of the Caribbean corals Siderastrea siderea, S. radians, and Pseudodiploria strigosa between the three thermal regimes. Siderastrea siderea associated with distinct Symbiodinium communities when compared to their congener S. radians as well as P. strigosa, demonstrating host-specificity of Symbiodinium along the MBRS. Symbiodinium community differences were only detected across thermal regimes for S. siderea; however, thermal parameters influenced Symbiodinium communities in all coral species investigated. Interestingly, Symbiodinium trenchi, a symbiont known to confer thermal tolerance, was dominant only in S. siderea at one sampled offshore site and was rare inshore, suggesting that coral thermal tolerance in more thermally variable inshore habitats is achieved through alternative mechanisms. Overall, thermal parameters alone were not the primary drivers of Symbiodinium community composition, suggesting that environmental variables unrelated to temperature (i.e., light availability, or nutrients) may play key roles in structuring coral-algal communities in Belize. %U https://www.biorxiv.org/content/biorxiv/early/2017/06/22/154179.full.pdf